LED matrix problem

[littletransistor]

Hey there,

I have a common anode 5x7 LED matrix and now I couldn't get all of these LED to light up at the same time (I 'lamp test' it). I had laid down the intricate details of multiplexing it, but with this wiring problem, I couldn't even get it to lit up a row properly.

The components wired are PIC16F628A and a decoder 74HCT138N.

RA0 - RA7 is wired to the rows (the 7s) and the RB0-RB2 is linked to the decoder A0-A2 and to the columns (the 5s) Y0-Y4.

Unfortunately, I can't get these to lit, or it lit in the wrong section. Any ideas how am I going to do around this? For now I couldn't get it to sink currents or whatsoever!

 

[blueroomelectronics]

It's a 3 to 8 demux, only one LED can light at a time. You have to refresh them > 50Hz to appear on all at once. It's also an active low demux...
Why are you running the cathodes back to a PIC I/O pin?

PS you don't have current limiting resistors AND you've shorted out all the LEDs.

 

[Nigel Goodwin]

I suggest you consult my PIC tutorials, which should how to multiplex 8x8 using a 16F628.